Blue Cat's FreqAnalyst Pro is an extended version of the freeware Blue Cat's FreqAnalyst.
Blue Cat's FreqAnalyst Pro is a real time spectrum analyzer with extremely smooth response and complete control over the audio spectrum analysis, including slope and offset correction. It offers memory slots to save/restore frequency response curves for easier A/B comparison and a customizable user interface with a transparency feature letting you see behind it. A spectrogram view has been added to the picture to monitor the evolution of the spectrum over time. Last but not least, this plug-in is able to extract frequency information from the audio signal and export it as MIDI CC or automation curves in real time: audio effects or MIDI hardware can now be controlled by the pitch of the signal.